The evaluation and assessment of the various sites are based on the following criteria: ecology of the site, size (area), accessibility and management.
The ecology of the site is the most important factor which will determine the success or failure of the farming activity in any site. Unfortunately, it is also the most difficult to assess. Synoptic evaluation of both the physico-chemical and biological characteristics of the site only gives one a superficial measure or basis which are then analyzed and interpreted in the light of one's past experience. While the exercise does not guarantee success, yet it narrows down the choices to a few which are most likely to succeed. Final decision on the choice of the site is through test planting on the site using the species to be farmed. Aside from accessibility of the site and management, the ecological factors utilized as bases in evaluation of the nine sites surveyed are the presence or absence of the local stocks, the water movement (current) in the area, the presence or absence of indicator species, the type of substratum, depth and the nature of the community.
A brief discussion of the relative importance of these different factors is made below.
(a) Local stocks
The availability of local stocks of the species to be cultured is one of the important factors to be considered in the evaluation of the site. The presence of local stocks in the site or in nearby areas eliminates the problem associated with the acquisition of seed stocks. The process of acquiring, transporting, acclimatizing and multiplying of planting materials when these are not available in the site is time consuming and can significantly delay the schedule of site development. It also entails the use of extra man-hours and sizeable amount of funds which could be very well used in the actual development. Besides, the presence of good local stocks is definitely a concrete evidence that the ecological conditions in the site are favourable for the growth and development of the species to be cultured.
(b) Water movement
Among the oceanographic factors which may be considered as a key factor in seaweed culture is water movement. This refers to the sum total of water motion that characterizes the site. Waves or currents facilitate nutrient transport and mixing. Well mixed water is homogenous and prevents extreme fluctuations of other factors such as temperature, salinity, pH, dissolve oxygen, etc. Accumulation of silt and epiphytes which may significantly hinder plant growth and development are also eliminated. In seaweed farming, however, current is considered a better form of water motion than waves. It is more predictable and generally unidirectional depending on the tidal conditions of ebb and flood. Waves are more destructive than currents.
Theoretically, the stronger the current the better, but it is only good up to a point where the support system of the farm or the plants are not destroyed. Fixed off-bottom type of farming is more prone to such destruction than the fixed bottom type. Based on Philippine experience, areas characterized by strong currents such as the Danajon Reef in Northern Bohol in the Visayas Region supports very high growth rates of E. spinosum. This area is presently the production centre for this species. Current speeds from 5 to 10 meters per minute have been recorded in this site. Loss due to breakage of the plants have been prevented by the construction of retaining nets at the leeward side of the farms.
(c) Indicator species
This criterion refers to species which can be used as indicators of general oceanographic conditions of the site or of the potentials of the site to support the species to be cultured. The abundance, for instance, of benthic coelenterates such as the soft corals is indicative of good water movements (currents). These animals are filter feeders and depend on food transported by currents. The importance of this oceanographic factor in the culture of E. spinosum is discussed above.
(d) Substratum
The type and nature of the substratum are important factors in site selection. These are both reflective of the oceanographic conditions of the reef as well as determine the degree of ease in the construction and development of the farm.
Areas which are too rocky are generally wave-exposed areas while those characterized by fine sand or silt are generally protected from any form of water motion. On the other hand, reef areas with coarse sandy bottom mixed with coral fragments are generally current washed areas. The substrate is generally firm under this condition.
Farm sites characterized by very hard and solid substrate will require more man-hours in the building of the support system of the farm, thus a significant amount of man-hours is wasted.
(e) Depth
Ideally the depth of the water in the farm site should range from 0.3 to 0.6 m during very low tides. This is important in relation to the ecological requirements of the species to be cultured as well as the ease by which the farmers can operate in the farm.
Natural stocks of Eucheuma, for instance, are generally found just below the zero tide level or slightly below it. These are exposed to air for an hour or so during extreme low tides. Exposure to air appears to be an ecological advantage especially when grazing pressure in the area is high. Predators are generally limited only to periods of high tides. Under such condition, the seaweed generally form thick clumps on the surface of the substratum. Growth proceeds laterally instead of upwards. In contrast stocks found in areas which are never exposed even during average low tides form erect robust thalli where growth proceeds both sidewards and upwards.
The latter tidal condition is most ideal in Eucheuma farming, thus areas where depth of the water is 0.3 to 0.6 m during extreme tides are most preferred.
Besides farm operations such as construction of the support system and planting will be much easier compared to deeper areas. Farmers can stand or walk in knee to waist deep water instead of swimming and diving such as the case in deeper areas and thus save energy.
(f) Nature of the community
This factor reflects the general ecological conditions of the site. In mature and stable communities, the diversity of species in the community is high and is reflected by the large variety of species in contrast to ecologically unstable areas. The latter is characterized by low species diversity where only few species are found.
Thus in site surveys where data on species diversity is not available, the evaluation of the ecological conditions may be based on the relative number of species found. The efficiency of this approach is dependent on the ability of the surveyor to recognize the various species.
(g) Other factors
These would include transparency of the water, pH, freshwater source and temperature.
Turbid waters have high silt load which reduces water transparency. Aside from hindering light penetration, silt may accumulate on the algal thalli and adversely affect growth and development of the plants. Such effects, however, may be nullified in areas where the current is moderate to strong. In well mixed waters, the problem of pH fluctuations is negligible and very seldom becomes a critical factor. The presence of freshwater sources such as rivers and streams in the vicinity of the site may significantly influence the salinity of the water in the farm site. The dilution effects of freshwater may however be nullified by the dominant current system. This will in turn affect the nature of the community and presence or absence of indicator species which are crucial in the evaluation of suitability of the site. Temperature is another factor which is also secondary. Problems associated with fluctuations in water temperature is nil as long as water mixing in the site is efficient.
This is an important consideration in relation to the future plans for expansion. A few hectares is ideal for a pilot farm site. However, consideration for future expansion for private farms in the site or nearby areas must be taken into consideration. The sites for private farm development must be preferably in the immediate vicinity of the pilot farm or at least these must be accessible from it. Extension service work will be much easier under this condition.
The site must be preferably accessible to agencies that can render technical assistance to the farm, either by water or land transport or both. Aside from savings in terms of transport fuel and time of the key personnel involved in the project, the distance of the pilot farms from the service offices will either encourage or discourage the personnel to visit or be in these farms. This factor is important in terms of management especially of the initial pilot farms.
This closely relates to the accessibility of the pilot farm site from the government or other service agencies involved in the project.
The team leader and staff for the pilot sites must spend a greater part of their time working on the various activities in the farm. One cannot efficiently manage a farm if he is detached from the project site. The accessibility of the pilot site is therefore important in this respect.
The results of the evaluation are presented in Table 1. The criteria were applied in the selection of the pilot sites for Eucheuma culture, and for the natural management of Gracilaria. Tablolong Reef and Serengan Island appear to be most suitable for Eucheuma while Pulau Dapi ranks first for Gracilaria (Table 1).
Three out of the nine sites surveyed are recommended for development, two for Eucheuma species culture and one for management of natural stocks and production of Gracilaria.
Two sites recommended for field testing of E. spinosum prior to actual development are the sites in the north channel fronting Serengan Island in Bali province and the Tablolong Reef in Kupang, East Nusa Tenggara province.
(a) Serengan Island North Channel, Bali province (Figure 2)
The area is characterized by highly diversed flora of which many species are indicators of good water movement, a primary oceanographic factor important in Eucheuma culture. Spot inspection of the site by skin diving corroborated this observation. The presence of eel grasses free of epiphytes and silt as well as the associated jointed coralline algae are additional evidences which are indicative of stable condition of this specific area in Serengan.
Although Eucheuma species is not present in the area, its introduction in the site is very feasible. Introduction of E. spinosum in Terura, Genoa, Bali has been successful inspite of the less favourable ecological conditions in that site.
Although the area selected is only 2 to 4 hectares in this site, it is large enough for a pilot farm. The site is very accessible from Denpasar for management purposes and seed stocks are available from Terura. Due to the irregular bottom contour, the site cannot be uniformly planted. It is, therefore, advisable that only portions deep enough are to be planted.
The site is also well-protected from the direct impact of waves by the outer reef which is more than half of a kilometer seawards. Other species of Eucheuma such as E. striatum can also be introduced in this site.
(b) Tablolong Reef in Kupang, East Nusa Tenggara province (Figure 8)
This site is quite impressive in terms of its farming potentials for E. spinosum. Both the biological and physical characteristics of the area appear to be most favourable for the culture of this species.
The site is large consisting of not less than 15 hectares of farmable area. The local current is moderate at the time of inspection to probably stronger during the SE monsoon season. According to local information, the site is never exposed with at least 30 cm of water during low tides. Actual observations during extreme tidal periods should be done to ascertain this.
Aside from its large size and favourable current system, the site has other major assets. The presence of a diverse biotic community, consisting of many species of seaweeds and animals which appear to be highly flourishing in the area, is indicative of a good and stable community. The presence of both live hard and soft coral patches towards the outer half of the reef and soft corals interspersed almost uniformly in the carpet of short and robust eel grasses consisting of at least three species towards the inner half of the reef is further evidence of good water movement, a primary factor in E. spinosum culture.
Many other favourable characteristics add to the good potentials of the site. The substratum of firmly compacted, coarse sand and coral fragments is most favourable for the construction of the support system of the farm. One of the added cost in comparable sites in the Philippines for E. spinosum farms is labour cost spent for building of the support system due to the hard and solid substratum. This problem will be minimal in Tablolong. Aside from this, the bottom is also uniform and flat throughout the inner half of the reef.
The site also supports a large stock of E. spinosum enough to start at least a half hectare farm. The presence of a good stock of this species is the most important criterion indicative of the very good potentials of this area as a pilot site. Its presence eliminates the problem of stock introduction and propagation but most important is the fact that its presence is evidence that the species will grow there.
The accessibility of the site from Kupang either by water or land transport is an advantage for the management of the site. E. striatum may also be introduced here.
The presence of a large natural stock of Gracilaria in Pulau Dapi reef, West Nusa Tenggara province, is indicative of its high potential as source of raw material for agar production. Although field survey was done only in Pulau Dapi reef, it is highly possible that the neighbouring reefs may also support good stocks of this seaweed. Follow-up surveys must be done to ascertain this. The area must be protected from over harvesting. The stocks are doing well at present since there is no demand for Gracilaria. However, this will not be the case once the demand is up. A management programme (pilot) is recommended for this area.
Due to major time and local (water) transport constraints, not all of the projected sites for survey were covered during this trip, thus additional surveys must be done on the following:
